Sleep Latency Test

Cairo University Medical School Hospitals, Cairo, Egypt CLETE A. KUSHIDA 

Excessive daytime sleeepiness (EDS) leads to impaired performance, diminished intellectual capacity, and is a major cause of accidents and other catastrophes (1). Thus, quantification of EDS is an important procedure, as positive findings willl require a thorough search and treatment of the cause or causes. The method of measurement, however, must be reliable and reproducible so that its results are respected in experimental and clinical settings. 

The technique most commonly used for objective evaluation of daytime sleepiness is the Multiple Sleep Latency Test (MSLT). It is composed of a series of naps during which subjects are asked not to resist sleep. The speed of falling asleep on tests across time is the chief outcome of the MSLT, which has achieved widespread acceptance because of its simple, intuitive approach to sleepiness. Hence, the greater levels of sleepiness are indicated by more rapid sleep onsets. Furthermore, the MSLT provides several opportunities to test for sleep-onset rapid-eye-movement (REM) episodes, the primary diagnostic sign of narcolepsy. 

in the mid-1970s, the Stanford group devised the MSLT and tested its usefulness, first in a study of sleep deprivation of the prototypical experimental psychology research subject, the normal college student. The timing of the MSLT was based on several considerations including  

The need for a repeated measure of sleep within a day for clinical evaluations. 

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FIGURE 38-1. Primary assessment and initial treatment for complaint of excessive daytime sleepiness. RLS, restless-legs syndrome NPSG, nocturnal polysomnography OSA, obstructive sleep apnea DA, dopamine agonist MSLT, multiple sleep latency test BZDRA, benzodiazepine receptor agonist SNRI, serotonin and norepinephrine reuptake inhibitor TCA, tricyclic antidepressant CPAP, continuous positive airway pressure. 

MSLT multiple sleep latency test KEY REFERENCES AND READINGS... 

Dement WC. Objective measurements of daytime sleepiness and performance comparing quazepam with flurazepam in two adult populations using the multiple sleep latency test. J Clin Psychiatry 1991 52(suppl 9) 31-37. 

To understand this principle, consider two examples (1) the natural time-window for sleep readiness, and (2) the natural time-window for hallucinatory activity. These are important to recognize if we wish either to promote sleep and/or to reduce hallucinosis. Some people suppose that they can fall asleep at any time, others that they can fall asleep only at one particular time. Both groups are wrong. Despite wide individual variation in sleep proneness—as measured by the multiple sleep latency test—there are both windows of opportunity (the mid to late afternoon) and forbidden zones (the mid evening) for sleep that affect all of us. I am sleepy now at 4 15 p.m., but four hours from now (at 8 15... 

Chervin R, Aldrich MS, Pickett R, Guilleminault C. Comparison of the results of Epworth Sleepiness Scale and multiple sleep latency test. J Psychosom Res 1997 42 145-155. 

Carskadon MA, Dement WC. The multiple sleep latency test what does it measure Sleep 1982 5 S67-S72. 

Carskadon MA, Dement WC. Multiple sleep latency tests during the constant routine. Sleepl992 15(5) 396-399. 

Chervin RD, Kraemer HC, Guilleminault C. Correlates of sleep latency on the multiple sleep latency test in a clinical population. Electroencephalog Clinical Neurophysiol 1995 95 147-153. 

Carskadon MA, Dement WC, Mitler MM, Roth T, Westbrook PR, Keenan S. Guidelines of the Multiple Sleep Latency Test (MSLT) a standard measure of sleepiness. Sleep 1986 9(4) 519-524. 

Bonnet MH, Arand DL. Sleepiness as measured by modified multiple sleep latency testing varies as a function of preceding activity. Sleep 1998 21 477-483. 

Benbadis SR, Perry M, Wolgamuth BR, Mendelson WB, Dinner DS. The multiple sleep latency test comparison of sleep onset criteria. Sleep 1996 8 632-636. 

Benbadis SR, Qu Y, Wames H, Dinner D, Perry M, Piedmonte M. Interrator reliability of the multiple sleep latency test. Electroencephalogr Clin Neurophysiol 1995 95 302-304. 

Mitler MM, Van den Hoed J, Carskadon MA, Richardson G, Park R, Guilleminault C, Dement WC. REM sleep episodes during the Multiple Sleep Latency Test in narcoleptic patients. Electroencephalogr Clin Neurophysiol 1979 46 479 481. 

Amira SA, Johnson TS, Logowitz NB. Diagnosis of narcolepsy using the Multiple Sleep Latency Test analysis of current laboratory criteria. Sleep 1985 8(4) 325-331. 

Aldrich MS, Chervin RD, Malow BA. Value of the Multiple Sleep Latency Test (MSLT) for the diagnosis of narcolepsy. Sleep 1997 20(8) 620-629. 

Reynolds CF, Coble PA, Kupfer DJ, Holzer BC. Application of multiple sleep latency test in disorders of excessive sleepiness. Electroencephalogr Clin Neurophysiol 1982 53(4) 443 L52. 

Sangal RB, Thomas L, Mitler MM. Maintenance of wakefulness test and Multiple Sleep Latency Test measurement of different abilities in patients with sleep disorders [see comments]. Chest 1992 101 898-902. 

In an earlier experiment, cumulative increases in PVT lapses across 7 days of sleep restricted to approximately 5 hr per night (29) were shown to be strongly related (r = -0.95) to sleep onset latency as assessed by the Multiple Sleep Latency Test (MSLT) in a nearly identical protocol (72). It appears that PVT performance lapse frequency and the well-validated physiological measure of sleep propensity may reflect the same basic process of escalating sleep pressure with sleep loss. 

Polysomnography has been used in both laboratory and home-based studies of children and adolescents to obtain measures of sleep and sleep-related events (10,25-31), and also measures of daytime sleepiness from the Multiple Sleep Latency Test (MSLT) procedure (11). Because polysomnography is so expensive, most of these studies have obtained only one or a few nights of study for cross-sectional samples of children and adolescents at different ages or devel-... 

In a laboratory-based study of sleepiness using the Multiple Sleep Latency Test (MSLT), hospital residents were found to be near the twilight zone following postcall (mean time to sleep of 5.5 min) (46). Perhaps most provocative was that their baseline (not on-call) level of sleepiness was not significantly different at 6.5 min. This demonstrated both the level of chronic sleep deprivation experienced (as reflected in the baseline condition) and the physiological level of sleepiness that can be expressed postcall. When the residents had the opportunity... 

Subjective (e.g., Epworth Sleepiness Scale) and objective [e.g., Multiple Sleep Latency Test (MSLT)] daytime somnolence quantification does not seem to provide valuable information on patients risks. This could be explained by the fact that sleep-related accidents occur at certain times when behavioral and chronobiological factors play an important role. Medical and legal issues could nevertheless require an objective test, such as the Maintenance of Wakefulness Test (MWT), to confirm that treated apneic patients present a normal level of vigilance. 

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